1. Field of the Invention
The present invention relates to a headlight unit for a vehicle, and more particularly to a headlight unit suitable for improving light distribution of a low and high beams, and for improving the diverse intensity between the two beam types.
2. Background Art
It is known that a pair of right and left headlights may be supported to a cowling provided at a front portion of a vehicle. Each headlight includes a low-beam emitting lamp located at a laterally inner portion of the vehicle and a high-beam emitting lamp located at a laterally outer portion of the vehicle. The cowling is provided for the purpose of reducing an air resistance on the front portion of the vehicle at high-speed running to thereby improve running performance. However, the lateral arrangement of four lamps causes an increase in width of the cowling, which is disadvantageous from the viewpoint of the reduction in air resistance and is poor in outward appearance. Particularly, in the case of intending to obtain a sufficient light quantity from each headlight, the expansive diameter of a reflector causes a further increase in the width of the cowling.
A motorcycle solving the above problem by adopting a projector type headlight has been proposed (Japanese Patent Laid-open No. Hei 2-136383). The projector type headlight has a configuration such that light reflected on a reflector is passed through a convex lens and projected forward, thus reducing the size of the reflector to reduce the width of the cowling.
In the above conventional headlights, the position of light emission changes between the low beam and the high beam, thereby offering improvement in accenting each beam""s intensity. However, since all the four lamps are light sources of the same kind, the accenting effect is low. Further, another problem is, it is difficult to obtain light distribution characteristics respectively suitable for the low beam and the high beam. That is, the low beam is required to illuminate a wide area at a relatively short distance, whereas the high beam is required to illuminate a narrow or spot area at a relatively long distance. However, such characteristics are difficult to obtain using conventional headlights.
Further, the projector type headlight has a problem such that its length along a beam axis is relatively large, so that the layout of parts, such as meters located behind the headlight, is limited.
It is accordingly an object of the present invention to provide a headlight unit for a vehicle which can improve the accenting effect in switching between the low beam and the high beam, can obtain proper light distribution characteristics for the low beam and the high beam, and can increase the degree of freedom of the layout of parts located behind the headlight.
In accordance with a first aspect of the present invention, there is provided a headlight unit for a vehicle, including a pair of right and left headlights provided at a front portion of the vehicle, each of the right and left headlights including a low-beam emitting lamp for emitting a low beam; a high-beam emitting lamp for emitting a high beam; a reflector having a reflector surface for reflecting the low beam emitted from the low-beam emitting lamp and a reflector surface for reflecting the high beam emitted from the high-beam emitting lamp; and a lens provided so as to commonly cover the low-beam emitting lamp and the high-beam emitting lamp; wherein the low-beam emitting lamp is located at a laterally inner position of the vehicle, and the high-beam emitting lamp is located at a laterally outer position of the vehicle higher in level than the low-beam emitting lamp; the reflector surface for the low-beam emitting lamp is larger in size than the reflector surface for the high-beam emitting lamp; and the lens has a laterally inner portion opposed to the reflector surface for the low-beam emitting lamp and a laterally outer portion opposed to the reflector surface for the high-beam emitting lamp, the laterally inner portion being larger in size than the laterally outer portion.
In accordance with a second aspect of the present invention, the low-beam emitting lamp comprises a discharge tube as a light source. In accordance with a third aspect of the present invention, the headlight unit further comprises a pair of right and left boosting devices interposed between the right and left headlights and respectively connected to the discharge tubes of the right and left headlights.
According to the first aspect, the low beam is reflected on the larger reflector surface to illuminate a wide area at a relatively short distance ahead of the vehicle, and the high beam is reflected on the smaller reflector surface to illuminate a narrow or spot area at a relatively long distance ahead of the vehicle. Further, the high beam and the low beam are directed at different heights, thereby obtaining a high accent effect in switching between the high beam and the low beam. Particularly, according to the second aspect, the discharge tube can produce strong light unlike a halogen lamp or the like, thereby allowing wide light distribution suitable for the low beam. Further, according to the third aspect, each boosting device is located near the corresponding discharge tube, so that a high-voltage shield wire required to ensure noise immunity can be shortened to thereby achieve more effective noise prevention. In addition, the boosting devices are located at a laterally central position of the vehicle, thereby obtaining a good balance of weight.
In accordance with a fourth aspect of the present invention, the reflector surface for the low-beam emitting lamp and the reflector surface of the high-beam emitting lamp are integrally formed; and each of the right and left headlights further comprises aiming means for pivotally moving the reflector in a vertical direction; a pivotal axis about which the reflector is pivotally moved being set in relation to the reflector surface for the low-beam emitting lamp so that a beam axis of the low-beam emitting lamp can be desirably adjusted. In accordance with a fifth aspect of the present invention, the aiming means comprises an electric motor for pivotally moving the reflector in the vertical direction.
According to the fourth aspect, the low beam whose luminous intensity is high can be accurately directed in a direction desired by an operator. Particularly, according to the fifth aspect, the aiming can be performed by the electric motor, thereby reducing the load on the operator and allowing accurate adjustment of the beam axis.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.